CONTACT CEPTORS 73 



equipped with protective reflexes whereby to withstand 

 all the harmful mechanical agencies that menace its 

 survival. The lack of protective response to the X-ray, 

 for instance, is but one of many similar instances of the 

 lack of protective mechanisms against lately evolved 

 menaces to human life. 



In the areas and organs which through the ages have 

 been most exposed to direct contact with environment, 

 we find the greatest number and the most complete 

 systems of adaptation to the common harmful and 

 beneficial agencies which are encountered in the en- 

 vironment. Thus, in the skin and exposed mucous 

 membranes we find the most plentiful distribution of 

 ceptors in those regions most open to environmental 

 contacts. In the mechanism for the protection of the 

 eye and the nose we have a symbolic suggestion of 

 perennial flying dust and debris, which always must 

 have imperiled the organism by assailing those im- 

 portant organs. In the abundant ceptors for touch on 

 the hand and for taste on the tongue, we have proof 

 that it was always at these points that objects to be 

 apprehended or swallowed were first encountered. 

 The location of the ceptor mechanisms tells a vivid story 

 of the development of the organism, of the chief dangers 

 which have threatened and the chief benefits which 

 have exerted a positive influence upon the survival of 

 the species. On the other hand, the absence of ceptors 

 gives equally suggestive testimony regarding the phy- 

 logeny of the species. On the basis of the presence 

 and the absence of ceptor mechanisms, therefore, we 

 may infer and reconstruct much of the past history of 

 the organism. 



